nfc: st-nci: Rename st21nfcb to st-nci

STMicroelectronics NFC NCI chips family is extending
with the new ST21NFCC using the AMS AS39230 RF booster.
The st21nfcb driver is relevant for this solution and
might be with future products.

Signed-off-by: Christophe Ricard <christophe-h.ricard@st.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>